The invention relates generally to a hydraulic valve-clearance compensating element for internal combustion engines, and more particularly to one of the type in which an internal valve stem is axially shiftable relative to an external stem and, together with the latter, delimits an oil-filled storage chamber, the volume of which may be altered and which is sealed to the outside by a gasket.
A hydraulic valve-clearance compensating element is disclosed in the German Published Patent Application no. 35 06 730. This device contains a storage chamber that is sealed off with respect to the outside by a gasket having a bellows-type construction and which is otherwise inflexibly defined. Its long-term durability is not very satisfactory; the device is particularly subject to gasket damage after a relatively short period of time.
Another valve-clearance compensating element is disclosed by the German Published Patent Application no. 28 47 699. It provides that several swell members be arranged adjacent to one another and incorporate an air cushion, dispersed finely between them. It is noteworthy, however, that both hydraulic fluid as well as a certain component of air are present in the storage chamber. The resultant working properties are not very satisfactory. Another variant provides that the air in the storage chamber be retained by glass spheres or by plastic pearls, or for the swell members to consist of a partially liquid-soaked, sponge-like material help to provide an air cushion, together with the specified component of air. This variant does not properly assure that the air components from the high-pressure chamber are kept out effectively.
The invention is directed to the problem of further developing a valve-clearance compensating element having a storage chamber that is sealed off to the outside, which can be produced cost-effectively and which has an enhanced service life as well as exhibiting improved working properties.